Conventionally, a trickle irrigation method is known as a method for culturing plants. In the trickle irrigation method, a trickle irrigation tube is disposed on the soil where plants are planted, and irrigation liquid such as water and liquid fertilizer is slowly dropped from the trickle irrigation tube to the soil. The trickle irrigation method can minimize the consumption amount of the irrigation liquid, and therefore has been increasingly attracting attention in recent years.
Normally, a trickle irrigation tube includes a tube in which a plurality of through holes for discharging irrigation liquid is formed, and a plurality of emitters (also called “drippers”) for discharging the irrigation liquid from the through holes. In addition, regarding the type of emitters, emitters which are joined to the inner wall surface of the tube (see, for example, PTL 1), and emitters which are inserted on the external side of the tube are known.
PTL 1 discloses an emitter that is joined to the inner wall surface of the tube. The emitter disclosed in PTL 1 includes a first member including a water inlet for taking the irrigation liquid, a second member including an outlet for discharging the irrigation liquid, and a film member disposed between the first member and the second member. In the first member, a valve seat part disposed to surround the water inlet, and a pressure reducing groove that serves as a part of pressure reducing channel are formed. In the film member, a through hole is formed at a position corresponding to the downstream end of the pressure reducing groove.
By stacking the first member, the film member and the second member, a pressure reducing channel is formed, and the film member makes contact with the valve seat part to close the water inlet. In addition, a channel through which the irrigation liquid flows from the water inlet to the outlet is formed.
In the emitter disclosed in PTL 1, when the pressure of the irrigation liquid in the tube is equal to or greater than a predetermined pressure, the film member closing the water inlet is pushed by the irrigation liquid, and the irrigation liquid flows into the emitter. The pressure of the irrigation liquid having entered the emitter is reduced by a reducing channel and the irrigation liquid is quantitatively discharged from the outlet.